Could I suggest the 50 f/1.4? I currently have both the 50f/1.4 and 50 f/1.8 II. I was able to take some photos I am very happy with using the 50 f/1.8 II. It is very sharp from f/2.8 to f/8. Very nice image quality. But the AF was slow and inconsistent. I am much happier with the AF on the 50 f/1.4, granted, it is still slow compared to my other lenses. In addition, I am pleased with the sharpness of the 50 f/1.4 from f/2 to f/8, so gained a stop.

I've never used the 40 mm, but have heard/read/seen good things. I would be concerned a little that f/2.8 won't be enough for indoor use. You would need good lighting.